GIS metal particle defect distributed detection system, terminal and storage medium

Abstract

The invention discloses a GIS (Gas Insulated Switchgear) metal particle defect distributed detection system, a terminal and a storage medium, a bidirectional interference structure is introduced, the system utilizes a forward light path and a reverse light path formed by light splitting of a first coupler, and light phase disturbance generated at a sound vibration action point can be propagated to an interference point along two directions respectively; a measurable time offset is formed due to propagation path differences. According to the system, on the basis of the time difference, the delay amount is accurately obtained through a cross-correlation algorithm, back calculation is carried out in combination with the length of the reference optical fiber and the length of the guide optical fiber, an acoustic emission event can be mapped to a specific position in an optical fiber path, and therefore high-precision, continuous and multi-point-synchronization-free defect positioning is achieved. Distributed sensing and a bidirectional optical path difference positioning mechanism are combined, so that the system not only can detect weak acoustic emission events, but also can accurately determine the actual position of a metal particle defect in a GIS (Geographic Information System), and the detection range, the positioning precision and the economical efficiency of the device are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of power equipment condition monitoring, and in particular to a GIS distributed detection system for metal particle defects, a terminal, and a storage medium. Background Technology

[0002] Gas-insulated switchgear (GIS) is widely used in medium and high voltage power transmission and transformation systems due to its small footprint, high insulation strength, and high operational reliability. However, early defects such as metal particles, insulator surface contamination, and surface discharge are easily generated during the manufacturing, transportation, installation, and long-term operation of GIS. Metal particles, under the influence of a high electric field, can exhibit jumping, secondary collisions, or partial discharges. These processes are often accompanied by high-frequency acoustic emission signals and structural vibrations. If not detected in time, they may induce local insulation breakdown, ultimately leading to a major GIS equipment accident. Therefore, early monitoring and location of metal particle defects is a crucial technical requirement for ensuring the safe operation of GIS.

[0003] Existing detection technologies mainly fall into two categories: electrical methods and acoustic methods. Electrical methods, such as UHF partial discharge detection and pulsed current methods, can capture the electromagnetic pulses generated by discharges. However, their signals are easily submerged by noise in the strong electromagnetic interference environment of substations, and they are not sensitive to weak discharges caused by the jumping of metal particles. Acoustic detection methods typically use piezoelectric ceramic sensors (PZTs) mounted on the GIS housing to capture acoustic emission signals. However, since PZTs are point sensors, their coverage is limited, requiring a large number of sensors to achieve full cavity monitoring, increasing wiring complexity and maintenance costs. Furthermore, it is difficult to achieve synchronous sampling between multiple sensors, making it difficult to effectively implement positioning algorithms based on propagation time difference.

[0004] In recent years, fiber optic sensing technology has been gradually introduced into the field of power equipment condition monitoring due to its strong resistance to electromagnetic interference, high sensitivity, and long-distance transmission advantages. However, most acoustic emission detection schemes based on fiber optic interferometry are still at the single-point monitoring stage, unable to achieve the distributed detection and precise positioning required in practical engineering. At the same time, existing interferometric structures usually only have a unidirectional optical path, making it difficult to extract time difference information related to spatial position from the phase signal, resulting in insufficient positioning capability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a distributed detection system, terminal and storage medium for GIS metal particle defects, so that the fiber optic array can respond to the acoustic emission signals generated by the jumping or partial discharge of metal particles at any location, so as to realize long-distance and continuous coverage monitoring.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A distributed detection system for metal particle defects in GIS, characterized in that it includes a laser emitter, a first coupler, a second coupler, a third coupler, a sensing optical path, a reference optical path, and a photodetector; The laser emitter is used to output optical signals; The first coupler is used to receive the optical signal and split the optical signal into a first beam and a second beam; The second coupler is used to receive the first beam and inject the first beam into the sensing optical path and the reference optical path respectively in a forward direction; The sensing optical path includes an optical fiber sensing array for detecting internal discharge signals of the GIS. The reference optical path includes an acousto-optic modulator for generating a reference signal; The third coupler is used to combine the optical signals transmitted in the forward direction from the sensing optical path and the reference optical path into a forward interference optical signal; The third coupler is also used to receive the second beam and inject the second beam into the sensing optical path and the reference optical path in reverse, respectively; the second coupler is also used to combine the optical signals transmitted in reverse by the sensing optical path and the reference optical path into a reverse interference optical signal; The photodetector is connected to the second coupler and the third coupler respectively, and is used to convert the forward interference light signal into a first AC component and the reverse interference light signal into a second AC component.

[0007] To solve the above-mentioned technical problems, the present invention adopts other technical solutions as follows: A storage medium, characterized in that the storage medium stores a computer program, which, when executed by a processor, implements the steps of a distributed detection method for metal particle defects in GIS.

[0008] To solve the above-mentioned technical problems, the present invention adopts other technical solutions as follows: A distributed detection terminal for GIS metal particle defects includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of a distributed detection method for GIS metal particle defects.

[0009] The beneficial effects of this invention are as follows: It provides a distributed detection system, terminal, and storage medium for GIS metal particle defects. A first coupler splits the optical signal output from a laser into a first beam and a second beam. The first beam is used to construct forward interference, and the second beam is used to construct reverse interference, resulting in a measurable time difference between the same acoustic signal propagating along two different paths, thus forming an interferometric detection system with positioning capabilities. The second coupler injects the first beam into the sensing optical path and the reference optical path respectively. The fiber optic sensing array in the sensing optical path undergoes slight elastic deformation under the acoustic vibration caused by metal particle agitation or surface discharge in the GIS shell, causing a change in the effective length of the fiber. This length change is manifested in the dynamic change of the interference light phase due to the optical phase's extreme sensitivity to external acoustic vibration changes, thus exhibiting extremely high detection sensitivity. The acousto-optic modulator in the reference optical path provides a frequency shift, ensuring that both forward and reverse interference optical signals are always in a demodulated state.

[0010] The third coupler combines the two forward optical signals to form a forward interference signal. Simultaneously, it receives the second beam from the first coupler and injects it back into the sensing and reference optical paths, thus forming a second interference signal. Because the forward and reverse beams propagate along different paths, the relative distances between the two beams and the acoustic vibration point are different, resulting in a natural time delay in the interference phase. The downstream photodetector outputs a first AC component and a second AC component, respectively. These two signals contain information about the interference phase changes in both directions, providing a basis for subsequent time difference calculations.

[0011] Based on the above principles, the beneficial effects of this invention are as follows: It provides a distributed detection system, terminal, and storage medium for GIS metal particle defects. It employs a fiber optic sensing array that can be continuously deployed along the outer surface of the GIS housing, making the entire fiber a continuous sensing medium capable of covering the entire length of the device or multiple cavity areas, thus forming a natural distributed acoustic sensing capability. Unlike traditional piezoelectric sensors, which can only perform discrete detection at fixed installation points, the fiber optic array can respond to acoustic emission signals generated by the jumping or partial discharge of metal particles at any location, achieving long-distance, continuous coverage monitoring. Furthermore, by introducing a bidirectional interference structure, the system utilizes the forward and reverse optical paths formed by the first coupler's beam splitting. The optical phase disturbance generated at the point of acoustic vibration propagates along the two directions to the interference point, resulting in a measurable time shift due to the difference in propagation paths. Based on this time difference, the system accurately calculates the delay using a cross-correlation algorithm, and then performs inverse calculations using the reference fiber length and the guide fiber length, mapping the acoustic emission event to a specific location in the fiber optic path, thereby achieving high-precision, continuous defect localization without the need for multi-point synchronization. By combining distributed sensing with a two-way optical path difference positioning mechanism, the system can not only detect weak acoustic emission events, but also accurately determine the actual location of metal particle defects within the GIS, significantly improving the detection range, positioning accuracy, and device economy. Attached Figure Description

[0012] Figure 1 This is an architecture diagram of a distributed detection system for metal particle defects in GIS according to an embodiment of the present invention; Figure 2 This is a flowchart of a distributed detection method for GIS metal particle defects in an embodiment of the present invention; Figure 3 This is a schematic diagram of an optical fiber sensing array in an embodiment of the present invention; Label Explanation: 1. Laser emitter; 2. Isolator; 3. First coupler; 4. Second coupler; 5. Third coupler; 6. Sensing optical path; 61. Fiber optic sensing array; 611. Mandrel; 612. Fiber optic cable; 7. Reference optical path; 71. Acousto-optic modulator; 8. Photodetector. Detailed Implementation

[0013] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0014] Among existing technologies, fiber optic acoustic emission (FAE) sensing technology has emerged as a potential alternative to PZT (partial discharge transducer). Intrinsic fiber optic interferometry-based AAE sensing technology, with its advantages of high sensitivity, good multiplexing performance, and simple sensor unit structure, is a popular approach for external partial discharge detection. For example, a Michelson interferometer-based AAE sensing system successfully detected partial discharge signals inside GIS (Gas Insulator); a Mach-Zehnder interferometer-based AAE sensing system increased sensor sensitivity through mandrel structure design; and a Sagnac interferometer-based AAE sensing system addressed the influencing factors on sensitivity, proposing a fiber optic sensor unit design based on polyetheretherketone (PEEK) material. Furthermore, other researchers have also reported on intrinsic fiber optic interferometry-based partial discharge acoustic emission sensing technology. These studies have accumulated experience for AAE detection based on fiber optic interferometry. However, a problem exists: most current research focuses only on improving the sensitivity of fiber optic sensors, neglecting research on sensor multiplexing performance. The reported sensing systems can only perform single-point detection, belonging to discrete sensing, and cannot achieve distributed sensing, greatly reducing the economic viability of fiber optic interferometry sensing technology.

[0015] To at least solve the above problems, please refer to Figure 1 This invention provides a distributed detection system for metal particle defects in GIS, including a laser emitter 1, a first coupler 3, a second coupler 4, a third coupler 5, a sensing optical path 6, a reference optical path 7, and a photodetector 8. The laser emitter 1 is used to output optical signals; The first coupler 3 is used to receive the optical signal and split the optical signal into a first beam and a second beam; The second coupler 4 is used to receive the first beam and inject the first beam into the sensing optical path 6 and the reference optical path 7 respectively in a forward direction; The sensing optical path 6 includes an optical fiber sensing array 61 for detecting internal discharge signals of the GIS; The reference optical path 7 includes an acousto-optic modulator 71 for generating a reference signal; The third coupler 5 is used to combine the optical signals transmitted in the forward direction by the sensing optical path 6 and the reference optical path 7 into a forward interference optical signal; The third coupler 5 is also used to receive the second beam and inject the second beam into the sensing optical path 6 and the reference optical path 7 in reverse respectively; the second coupler 4 is also used to combine the optical signals transmitted in reverse by the sensing optical path 6 and the reference optical path 7 into a reverse interference optical signal. The photodetector 8 is connected to the second coupler 4 and the third coupler 5 respectively, and is used to convert the forward interference light signal into a first AC component and the reverse interference light signal into a second AC component.

[0016] As described above, the beneficial effects of this invention are as follows: The optical signal output from the laser is split into a first beam and a second beam via a first coupler. The first beam is used to construct forward interference, and the second beam is used to construct reverse interference, resulting in a measurable time difference between the same acoustic signal propagating along two different paths, thus forming an interferometric detection system with positioning capabilities. The second coupler injects the first beam into the sensing optical path and the reference optical path respectively. The fiber optic sensing array in the sensing optical path undergoes slight elastic deformation under the acoustic vibration caused by the jumping of metal particles or surface discharge in the GIS shell, causing a change in the effective length of the fiber. This length change is manifested in the dynamic change of the interference light phase through the characteristic that the optical phase is extremely sensitive to changes in external acoustic vibration, thus exhibiting extremely high detection sensitivity. The acousto-optic modulator in the reference optical path provides a frequency shift, ensuring that the forward and reverse interference optical signals are always in a demodulated state.

[0017] The third coupler combines the two forward optical signals to form a forward interference signal. Simultaneously, it receives the second beam from the first coupler and injects it back into the sensing and reference optical paths, thus forming a second interference signal. Because the forward and reverse beams propagate along different paths, the relative distances between the two beams and the acoustic vibration point are different, resulting in a natural time delay in the interference phase. The downstream photodetector outputs a first AC component and a second AC component, respectively. These two signals contain information about the interference phase changes in both directions, providing a basis for subsequent time difference calculations.

[0018] Based on the above principles, the beneficial effects of this invention are as follows: By employing a fiber optic sensing array that can be continuously deployed along the outer surface of the GIS housing, the entire fiber becomes a continuous sensing medium, capable of covering the entire length of the device or multiple cavity areas, thus forming a natural distributed acoustic sensing capability. Unlike traditional piezoelectric sensors, which can only perform discrete detection at fixed installation points, the fiber optic array can respond to acoustic emission signals generated by the jumping of metal particles or partial discharge at any location, achieving long-distance, continuous coverage monitoring. Furthermore, by introducing a bidirectional interference structure, the system utilizes the forward and reverse optical paths formed by the first coupler's beam splitting. The optical phase disturbance generated at the point of acoustic vibration will propagate to the interference point in two directions, resulting in a measurable time shift due to the difference in propagation paths. Based on this time difference, the system accurately calculates the delay using a cross-correlation algorithm, and then performs inverse calculations using the reference fiber length and the guide fiber length, mapping the acoustic emission event to a specific location in the fiber optic path, thereby achieving high-precision, continuous defect localization without the need for multi-point synchronization. By combining distributed sensing with a two-way optical path difference positioning mechanism, the system can not only detect weak acoustic emission events, but also accurately determine the actual location of metal particle defects within the GIS, significantly improving the detection range, positioning accuracy, and device economy.

[0019] Please refer to Figure 2 In some embodiments, a distributed detection method for GIS metal particle defects is performed, the method comprising the steps of: S1. Obtain the first AC component and the second AC component, and perform phase adjustment on the first AC component and the second AC component to obtain the first orthogonal reference signal and the second orthogonal reference signal; S2. Based on the first orthogonal reference signal and the second orthogonal reference signal, the time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method; S3. Obtain the reference fiber length between the second coupler and the third coupler, and the guide fiber length between the first coupler and the third coupler. Calculate the fiber distance between the acoustic signal application point and the second coupler based on the time difference. The acoustic signal application point is used to represent the location of the acoustic signal generated by metal particle defects in the GIS. S4. Based on the optical fiber distance between the point of action of the acoustic signal and the second coupler, the location of metal particle defects in the GIS is realized.

[0020] As described above, by introducing phase demodulation and time difference calculation steps based on AC components, the system is transformed from a simple optical path structure into a complete detection scheme capable of signal processing, data extrapolation, and defect localization. When the fiber optic sensing array is subjected to acoustic emission caused by the agitation of metal particles or partial discharge within the GIS, the effective length of the fiber undergoes a slight change. This perturbation ultimately manifests as a dynamic change in the phase of the interference light. The forward and reverse interference lights arrive at the photodetector at different times due to their different propagation directions, thus forming a first AC component and a second AC component containing phase differences.

[0021] In step S1, the system converts the high-frequency interference signal into a processable orthogonal baseband signal through phase modulation, transforming the original AC signal containing a fast carrier component into a low-frequency characteristic that directly reflects optical phase disturbances. It is through this orthogonal demodulation that the system is able to separate stable phase information from noise, light intensity fluctuations, and coupling inhomogeneities.

[0022] Subsequently, step S2 performs cross-correlation calculations on the two phase change waveforms based on the orthogonal reference signal. Cross-correlation essentially involves finding the most consistent time offset between the two phase curves through sliding matching, thus reliably extracting the arrival time difference of the forward and reverse interference signals in a real-world noisy environment. Since the position of the acoustic emission event on the fiber optic path determines the propagation distance of light from the event point to the interference point, and the propagation distance directly determines the occurrence time of the phase disturbance, the time difference becomes the core parameter reflecting the spatial location of the acoustic signal. Step S3 uses the reference fiber length and guide fiber length determined during system installation to convert the time difference into the fiber distance between the acoustic signal's point of action and the second coupler, achieving positioning in the optical path coordinate sense. Finally, step S4 maps this distance to the actual defect location within the GIS, enabling the system to continuously monitor, locate in real-time, and without requiring multi-sensor synchronization. Therefore, this claim achieves a complete process from optical phase disturbance extraction to defect location through a complete processing link, giving the system engineering usability and high-precision diagnostic capabilities.

[0023] In some implementations, the calculation formulas for the first AC component and the second AC component in step S1 are as follows:

[0024] In the formula, This is the first communication component; This is the second communication component; U 0 represents the amplitude of the AC component of the interference optical signal. f 0 represents the frequency shift amount of the acousto-optic modulator. This refers to the change in phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array. and These represent the initial phases of the forward and reverse interference optical signals, respectively. τ The time difference between the forward interference light signal and the reverse interference light signal is denoted as .

[0025] As described above, by providing mathematical expressions for the first and second AC components, the structural characteristics of the interference signal can be clearly modeled. The difference between forward and reverse interference lies precisely in the different times when the phase perturbation occurs. Because... The phase shift is caused by the slight deformation of the optical fiber at the point of acoustic emission, resulting in a relative time shift in the interference between the forward and reverse paths. τ It is the core information for positioning.

[0026] Using this mathematical relationship, the system can, according to and The waveform directly determines whether the frequency, amplitude, and phase structure of the interfering light are normal, thereby monitoring the stability of the light source, coupler performance, and fiber condition during operation. Furthermore, the explicit mathematical form also allows for the determination of the phase characteristics of the backpropagating light. This allows the demodulator to accurately identify the data, creating the necessary theoretical basis for cross-correlation calculations. Through this expression, the debuggability, analyzability, and repeatability of the interferometric positioning system are significantly enhanced, ensuring that the algorithm can accurately extract the relationship between phase change and time delay in engineering applications, thereby improving the accuracy of defect location.

[0027] In some embodiments, the change in the phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array is expressed as follows:

[0028] In the formula, λ Δ represents the wavelength of light. L This represents the difference in fiber length between the sensing optical path and the reference optical path.

[0029] As described above, optical fiber, as an elastic medium, undergoes extremely small axial expansion and contraction under external acoustic emission excitation. Although the amplitude of this expansion and contraction is extremely small, it can be infinitely amplified through the phase accumulation effect of light. When a light wave propagates in an optical fiber, the path length changes by Δ. L It will directly cause phase change Phase changes can be extremely noticeable in an interferometric optical field. This quantization relationship allows the system to detect minute mechanical perturbations that are orders of magnitude higher than those detected by mechanical sensors using optical phase.

[0030] In some implementations, in step S1, the first orthogonal reference signal and the second orthogonal reference signal are represented as follows:

[0031] In the formula, This is the first orthogonal reference signal; for The derivative of represents the first orthogonal reference signal; R 0 represents the amplitude of the reference signal.

[0032] As can be seen from the above description, the above... and The orthogonal structure enables the system to perform phase demodulation of interferometric optical signals in a mathematically stable and interference-resistant manner. By constructing a cosine reference signal with the same frequency as the interferometric carrier and an orthogonal reference signal with a 90-degree phase difference, the system can project the interferometric optical signal containing phase perturbations onto two mutually orthogonal components. This orthogonal projection ensures that the system can independently extract the two baseband components, I(t) and Q(t). Since these two components correspond to sine and cosine calculation formulas respectively, their combination is unique, and phase information can be stably recovered under conditions of amplitude drift, light intensity fluctuation, and noise interference. The setting of the orthogonal reference signal constructs the mathematical basis for the system's phase demodulation, enabling the system to extract effective phase changes from complex interferometric signals in a high-precision and robust manner, providing a reliable foundation for subsequent time difference calculations.

[0033] In some implementations, step S2 specifically includes: Based on the first orthogonal reference signal and the second orthogonal reference signal, the first AC component and the second AC component are respectively low-pass filtered to obtain the first baseband signal group and the second baseband signal group; The changes in the phase of the forward interference light and the changes in the phase of the reverse interference light are calculated using the first baseband signal group and the second baseband signal group, respectively. The time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method based on the change in the phase of the forward interference light and the change in the phase of the reverse interference light.

[0034] The first AC component converted from the forward interference optical signal For example, the process is as follows: Will respectively with 、 Multiply and then pass through the cutoff frequency f 1 f A low-pass filter with a value of 0 is used to filter out high-frequency components, resulting in the first baseband signal group:

[0035] In the formula, This indicates that the interfering light signal is in relation to the reference signal. The baseband component obtained by projection in the same phase direction; This indicates that the interference light signal is in the reference signal The baseband component obtained by projection onto the orthogonal directions (i.e., 90° out of phase); After performing differentiation-cross-multiplication on the first baseband signal group and taking the difference, we can obtain:

[0036] To eliminate the influence of signal amplitude, M (t) divided by , The sum of squares can be obtained

[0037] Assumption remain unchanged. Integrating the expression yields the change in phase of the forward interference light.

[0038]

[0039] in, , It is the result of the calculation process and has no physical meaning. Similarly, the second AC component of the reverse interference optical signal conversion can be obtained. The change in phase of the reverse interference light ; The time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method based on the change in the phase of the forward interference light and the change in the phase of the reverse interference light.

[0040] In some embodiments, in step S3, the calculation of the optical fiber distance between the point of action of the acoustic signal and the second coupler is performed according to the following formula:

[0041] In the formula, The reference fiber length between the second and third couplers; The length of the guiding fiber between the first coupler and the third coupler; The speed of light in an optical fiber; The distance between the point of application of the acoustic signal and the optical fiber of the second coupler is denoted as .

[0042] As described above, the forward and reverse interference light propagate along different paths in the optical fiber, resulting in different propagation times from the acoustic emission point to the interference point. This delay relationship caused by the optical path difference can be accurately characterized by the above equation, where... and Let τ be a fixed system parameter, and x be the location of the acoustic signal's point of application. By inverting this formula, τ can be directly converted into the spatial location x, thus mapping time information to length information and ultimately achieving positioning. The linear structure in the above formula makes the positioning process simple, stable, and less susceptible to system errors. When changes in fiber length or ambient temperature cause changes in the speed of light, the error will increase due to the symmetry of the forward and reverse structures. The mutual cancellation of these factors gives the system a natural resistance to temperature drift. Since the calculation process does not require multi-point synchronous sampling or rely on absolute phase, only a time difference is needed for positioning, thus significantly simplifying the system structure and improving reliability. This mathematical relationship establishes a scalable, calibrable, and long-term stable positioning mechanism for distributed fiber optic sensing systems, enabling this system to achieve positioning performance superior to traditional piezoelectric arrays.

[0043] In some embodiments, an isolator 2 is also included, which is located at the output end of the laser emitter 1 and is used to inject the optical signal output by the laser emitter 1 into the first coupler 3.

[0044] As described above, by placing an isolator at the output end of the laser transmitter, the system's stability and anti-interference capabilities are significantly enhanced. Since fiber optic connectors, couplers, and the ends of the optical path inevitably generate a certain amount of reflected light, this reflected light, if not blocked by an isolator, will flow back into the laser cavity, causing laser mode jumps, frequency drift, and even damage to the laser source. The isolator's unidirectional transmission characteristic ensures that light can only flow from the laser to the optical path and cannot return from the optical path to the source, thus keeping the laser operating under stable conditions.

[0045] A storage medium storing a computer program that, when executed by a processor, implements the steps of a distributed detection method for metal particle defects in GIS.

[0046] A distributed detection terminal for GIS metal particle defects includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of a distributed detection method for GIS metal particle defects.

[0047] Please refer to Figure 1Embodiment 1 of the present invention is as follows: A distributed detection system for metal particle defects in GIS includes a laser emitter 1, an isolator 2, a first coupler 3, a second coupler 4, a third coupler 5, a sensing optical path 6, a reference optical path 7, and a photodetector 8. The laser emitter 1 is used to output an optical signal; the isolator 2 is disposed at the output end of the laser emitter 1, and the isolator 2 is used to inject the optical signal output by the laser emitter 1 into the first coupler 3; The first coupler 3 is used to receive the optical signal and split the optical signal into a first beam and a second beam; The second coupler 4 is used to receive the first beam and inject the first beam into the sensing optical path 6 and the reference optical path 7 respectively in a forward direction; The sensing optical path 6 includes a fiber optic sensing array 61 for detecting internal discharge signals of the GIS; please refer to... Figure 3 The fiber optic sensing array 61 includes multiple sensing units, each sensing unit including a spindle 611 and an optical fiber 612, the optical fiber being wound around the spindle, and the bottom surface of the spindle being in contact with the object being measured; the multiple sensing units are connected in series. The reference optical path 7 includes an acousto-optic modulator 71 for generating a reference signal; The third coupler 5 is used to combine the optical signals transmitted in the forward direction by the sensing optical path 6 and the reference optical path 7 into a forward interference optical signal; The third coupler 5 is also used to receive the second beam and inject the second beam into the sensing optical path 6 and the reference optical path 7 in reverse respectively; the second coupler 4 is also used to combine the optical signals transmitted in reverse by the sensing optical path 6 and the reference optical path 7 into a reverse interference optical signal. The photodetector 8 is connected to the second coupler 4 and the third coupler 5 respectively, and is used to convert the forward interference light signal into a first AC component and the reverse interference light signal into a second AC component.

[0048] The operating principle of the above system is as follows: The optical signal output from the laser is split into a first beam and a second beam via a first coupler. The first beam is used to construct forward interference, and the second beam is used to construct reverse interference, resulting in a measurable time difference between the same acoustic signal propagating along two different paths, thus forming an interferometric detection system with positioning capabilities. The second coupler injects the first beam into the sensing optical path and the reference optical path respectively. The fiber optic sensing array in the sensing optical path undergoes slight elastic deformation under the acoustic vibration caused by the jumping of metal particles or surface discharge in the GIS shell, causing a change in the effective length of the fiber. This length change is manifested in the dynamic change of the phase of the interferometric light through the characteristic that the optical phase is extremely sensitive to changes in external acoustic vibration, thus exhibiting extremely high detection sensitivity. The acousto-optic modulator in the reference optical path provides a frequency shift, ensuring that the forward and reverse interferometric optical signals are always in a demodulated state.

[0049] The third coupler combines the two forward optical signals to form a forward interference signal. Simultaneously, it receives the second beam from the first coupler and injects it back into the sensing and reference optical paths, thus forming a second interference signal. Because the forward and reverse beams propagate along different paths, the relative distances between the two beams and the acoustic vibration point are different, resulting in a natural time delay in the interference phase. The downstream photodetector outputs a first AC component and a second AC component, respectively. These two signals contain information about the interference phase changes in both directions, providing a basis for subsequent time difference calculations.

[0050] This involves employing a fiber optic sensor array that can be continuously deployed along the outer surface of the GIS housing, making the entire fiber a continuous sensing medium capable of covering the entire length of the device or multiple cavity areas, thus forming a natural distributed acoustic sensing capability. Unlike traditional piezoelectric sensors, which can only perform discrete detection at fixed installation points, the fiber optic array can respond to acoustic emission signals generated by the jumping of metal particles or partial discharge at any location, achieving long-distance, continuous coverage monitoring. Furthermore, by introducing a bidirectional interference structure, the system utilizes the forward and reverse optical paths formed by the first coupler's beam splitting. The optical phase disturbance generated at the point of acoustic vibration propagates along the two directions to the interference point, creating a measurable time shift due to the difference in propagation paths. Based on this time difference, the system accurately calculates the delay using a cross-correlation algorithm, and then performs inverse calculations using the reference and guide fiber lengths to map the acoustic emission event to a specific location in the fiber optic path, thereby achieving high-precision, continuous defect localization without the need for multi-point synchronization. By combining distributed sensing with a two-way optical path difference positioning mechanism, the system can not only detect weak acoustic emission events, but also accurately determine the actual location of metal particle defects within the GIS, significantly improving the detection range, positioning accuracy, and device economy.

[0051] Please refer to Figure 2The above system implements a distributed detection method for metal particle defects in GIS, the method comprising the following steps: S1. Obtain the first AC component and the second AC component, and perform phase adjustment on the first AC component and the second AC component to obtain the first orthogonal reference signal and the second orthogonal reference signal; The calculation formulas for the first AC component and the second AC component are as follows:

[0052] In the formula, This is the first communication component; This is the second communication component; U 0 represents the amplitude of the AC component of the interference optical signal. f 0 represents the frequency shift amount of the acousto-optic modulator. This refers to the change in phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array. and These represent the initial phases of the forward and reverse interference optical signals, respectively. τ The time difference between the forward interference light signal and the reverse interference light signal is denoted as .

[0053] The change in the phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array is expressed as follows:

[0054] In the formula, λ Δ represents the wavelength of light. L This represents the difference in fiber length between the sensing optical path and the reference optical path.

[0055] By providing mathematical expressions for the first and second AC components, the structural characteristics of the interference signal are clearly modeled. The difference between forward and reverse interference lies precisely in the different times when the phase perturbation occurs. Because... The phase shift is caused by the slight deformation of the optical fiber at the point of acoustic emission, resulting in a relative time shift in the interference between the forward and reverse paths. τ It is the core information for positioning.

[0056] In step S1, the first orthogonal reference signal and the second orthogonal reference signal are represented as follows:

[0057] In the formula, This is the first orthogonal reference signal; for The derivative of represents the first orthogonal reference signal; R 0 represents the amplitude of the reference signal.

[0058] S2. Based on the first orthogonal reference signal and the second orthogonal reference signal, the time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method; Step S2 specifically includes: Based on the first orthogonal reference signal and the second orthogonal reference signal, the first AC component and the second AC component are respectively low-pass filtered to obtain the first baseband signal group and the second baseband signal group; The changes in the phase of the forward interference light and the changes in the phase of the reverse interference light are calculated using the first baseband signal group and the second baseband signal group, respectively. The time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method based on the change in the phase of the forward interference light and the change in the phase of the reverse interference light.

[0059] The first AC component converted from the forward interference optical signal For example, the process is as follows: Will respectively with 、 Multiply and then pass through the cutoff frequency f 1 f A low-pass filter with a value of 0 is used to filter out high-frequency components, resulting in the first baseband signal group:

[0060] In the formula, This indicates that the interfering light signal is in relation to the reference signal. The baseband component obtained by projection in the same phase direction; This indicates that the interference light signal is in the reference signal The baseband component obtained by projection onto the orthogonal directions (i.e., 90° out of phase); After performing differentiation-cross-multiplication on the first baseband signal group and taking the difference, we can obtain:

[0061] To eliminate the influence of signal amplitude, M (t) divided by , The sum of squares can be obtained

[0062] Assumption remain unchanged. Integrating the expression yields the change in phase of the forward interference light. ,

[0063] in, , It is the result of the calculation process and has no physical meaning. Similarly, the second AC component of the reverse interference optical signal conversion can be obtained. The change in phase of the reverse interference light ; The time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method based on the change in the phase of the forward interference light and the change in the phase of the reverse interference light.

[0064] S3. Obtain the reference fiber length between the second coupler and the third coupler, and the guide fiber length between the first coupler and the third coupler. Calculate the fiber distance between the acoustic signal application point and the second coupler based on the time difference. The acoustic signal application point is used to represent the location of the acoustic signal generated by metal particle defects in the GIS. In step S3, the optical fiber distance between the acoustic signal's point of action and the second coupler is calculated using the following formula:

[0065] In the formula, The reference fiber length between the second and third couplers; The length of the guiding fiber between the first coupler and the third coupler; The speed of light in an optical fiber; The distance between the point of application of the acoustic signal and the optical fiber of the second coupler is denoted as .

[0066] That is, the forward and reverse interfering light propagates along different paths in the optical fiber, resulting in different propagation times from the acoustic emission point to the interference point. This delay relationship caused by the optical path difference can be accurately characterized by the above equation, where... and Here, are fixed system parameters, and x is the location of the acoustic signal's point of application that needs to be determined. By inverting this formula, the... τ This is directly converted into spatial location x, thus mapping time information to length information, ultimately achieving positioning. The linear structure in the above formula makes the positioning process simple, stable, and less susceptible to systematic errors. When changes in fiber length or ambient temperature cause changes in the speed of light, due to the symmetry of the forward and reverse structures, the error will... The mutual cancellation of these factors gives the system a natural resistance to temperature drift. Since the calculation process does not require multi-point synchronous sampling or rely on absolute phase, only a time difference is needed for positioning, thus significantly simplifying the system structure and improving reliability. This mathematical relationship establishes a scalable, calibrable, and long-term stable positioning mechanism for distributed fiber optic sensing systems, enabling this system to achieve positioning performance superior to traditional piezoelectric arrays.

[0067] S4. Based on the optical fiber distance between the point of action of the acoustic signal and the second coupler, the location of metal particle defects in the GIS is realized.

[0068] In this embodiment, by introducing phase demodulation and time difference calculation steps based on AC components, the system is upgraded from a simple optical path structure to a complete detection scheme capable of signal processing, data extrapolation, and defect localization. When the fiber optic sensing array is subjected to acoustic emission caused by the agitation of metal particles or partial discharge within the GIS, the effective length of the fiber undergoes a slight change. This perturbation ultimately manifests as a dynamic change in the phase of the interference light. The forward and reverse interference light arrive at the photodetector at different times due to their different propagation directions, thus forming a first AC component and a second AC component containing phase differences.

[0069] In step S1, the system converts the high-frequency interference signal into a processable orthogonal baseband signal through phase modulation, transforming the original AC signal containing a fast carrier component into a low-frequency characteristic that directly reflects optical phase disturbances. It is through this orthogonal demodulation that the system is able to separate stable phase information from noise, light intensity fluctuations, and coupling inhomogeneities.

[0070] Subsequently, step S2 performs cross-correlation calculations on the two phase change waveforms based on the orthogonal reference signal. Cross-correlation essentially involves finding the most consistent time offset between the two phase curves through sliding matching, thus reliably extracting the arrival time difference of the forward and reverse interference signals in a real-world noisy environment. Since the position of the acoustic emission event on the fiber optic path determines the propagation distance of light from the event point to the interference point, and the propagation distance directly determines the occurrence time of the phase disturbance, the time difference becomes the core parameter reflecting the spatial location of the acoustic signal. Step S3 uses the reference fiber length and guide fiber length determined during system installation to convert the time difference into the fiber distance between the acoustic signal's point of action and the second coupler, achieving positioning in the optical path coordinate sense. Finally, step S4 maps this distance to the actual defect location within the GIS, enabling the system to continuously monitor, locate in real-time, and without requiring multi-sensor synchronization. Therefore, this claim achieves a complete process from optical phase disturbance extraction to defect location through a complete processing link, giving the system engineering usability and high-precision diagnostic capabilities.

[0071] Please refer to Figure 2Embodiment two of the present invention is as follows: A storage medium storing a computer program that, when executed by a processor, implements the steps of a distributed detection method for metal particle defects in GIS.

[0072] A distributed detection terminal for GIS metal particle defects includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of a distributed detection method for GIS metal particle defects.

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A distributed detection system for metal particle defects in GIS, characterized in that, It includes a laser emitter, a first coupler, a second coupler, a third coupler, a sensing optical path, a reference optical path, and a photodetector; The laser emitter is used to output optical signals; The first coupler is used to receive the optical signal and split the optical signal into a first beam and a second beam; The second coupler is used to receive the first beam and inject the first beam into the sensing optical path and the reference optical path respectively in a forward direction; The sensing optical path includes an optical fiber sensing array for detecting internal discharge signals of the GIS. The reference optical path includes an acousto-optic modulator for generating a reference signal; The third coupler is used to combine the optical signals transmitted in the forward direction from the sensing optical path and the reference optical path into a forward interference optical signal; The third coupler is also used to receive the second beam and inject the second beam into the sensing optical path and the reference optical path in reverse, respectively; the second coupler is also used to combine the optical signals transmitted in reverse by the sensing optical path and the reference optical path into a reverse interference optical signal; The photodetector is connected to the second coupler and the third coupler respectively, and is used to convert the forward interference light signal into a first AC component and the reverse interference light signal into a second AC component.

2. The GIS-based distributed detection system for metal particle defects according to claim 1, characterized in that, A distributed detection method for metal particle defects in GIS is implemented, the method comprising the following steps: S1. Obtain the first AC component and the second AC component, and perform phase adjustment on the first AC component and the second AC component to obtain the first orthogonal reference signal and the second orthogonal reference signal; S2. Based on the first orthogonal reference signal and the second orthogonal reference signal, the time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method; S3. Obtain the reference fiber length between the second coupler and the third coupler, and the guide fiber length between the first coupler and the third coupler. Calculate the fiber distance between the acoustic signal application point and the second coupler based on the time difference. The acoustic signal application point is used to represent the location of the acoustic signal generated by metal particle defects in the GIS. S4. Based on the optical fiber distance between the point of action of the acoustic signal and the second coupler, the location of metal particle defects in the GIS is realized.

3. The GIS distributed detection system for metal particle defects according to claim 2, characterized in that, In step S1, the calculation formulas for the first AC component and the second AC component are as follows: In the formula, This is the first communication component; This is the second communication component; U 0 represents the amplitude of the AC component of the interference optical signal. f 0 represents the frequency shift amount of the acousto-optic modulator. This refers to the change in phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array. and These represent the initial phases of the forward and reverse interference optical signals, respectively. τ The time difference between the forward interference light signal and the reverse interference light signal is denoted as .

4. The GIS-based distributed detection system for metal particle defects according to claim 3, characterized in that, The change in the phase of the interferometric light caused by the external acoustic signal acting on the fiber optic sensing array is expressed as follows: In the formula, λ Δ represents the wavelength of light. L This represents the difference in fiber length between the sensing optical path and the reference optical path.

5. A distributed detection system for GIS metal particle defects according to claim 3, characterized in that, In step S1, the first orthogonal reference signal and the second orthogonal reference signal are represented as follows: In the formula, This is the first orthogonal reference signal; for The derivative of represents the first orthogonal reference signal; R 0 represents the amplitude of the reference signal.

6. The GIS-based distributed detection system for metal particle defects according to claim 2, characterized in that, Step S2 specifically includes: Based on the first orthogonal reference signal and the second orthogonal reference signal, the first AC component and the second AC component are respectively low-pass filtered to obtain the first baseband signal group and the second baseband signal group; The changes in the phase of the forward interference light and the changes in the phase of the reverse interference light are calculated using the first baseband signal group and the second baseband signal group, respectively. The time difference between the forward interference light signal and the reverse interference light signal is obtained by using the cross-correlation calculation method based on the change in the phase of the forward interference light and the change in the phase of the reverse interference light.

7. The GIS distributed detection system for metal particle defects according to claim 3, characterized in that, In step S3, the optical fiber distance between the acoustic signal's point of action and the second coupler is calculated using the following formula: In the formula, The reference fiber length between the second and third couplers; The length of the guiding fiber between the first coupler and the third coupler; The speed of light in an optical fiber; The distance between the point of application of the acoustic signal and the optical fiber of the second coupler is denoted as .

8. The GIS distributed detection system for metal particle defects according to claim 1, characterized in that, It also includes an isolator, which is located at the output end of the laser emitter and is used to inject the optical signal output by the laser emitter into the first coupler.

9. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the distributed detection method for GIS metal particle defects according to any one of claims 2-7.

10. A distributed detection terminal for GIS metal particle defects, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the distributed detection method for GIS metal particle defects according to any one of claims 2-7.

Images